Q. Factor the expression completely.x4−10x2+21Answer:
Identify Type and Strategy: Identify the type of polynomial and look for a common factoring strategy.This is a quadratic in form, with x4 as the "squared" term, x2 as the "linear" term, and 21 as the constant. We can treat x2 as a single variable and factor it as if it were a quadratic equation.
Set Up Factoring Format: Set up the expression in a factoring format.We are looking for two binomials that multiply to give x4−10x2+21. The general form will be (x2−a)(x2−b), where a and b are numbers that multiply to 21 and add up to 10.
Find Factors and Sum: Find the factors of 21 that add up to 10. The factors of 21 are 1, 3, 7, and 21. The pair that adds up to 10 is 3 and 7.
Write Factored Form: Write the factored form using the factors found.The factored form of the expression is (x2−3)(x2−7).
Check Factoring: Check the factoring by expanding the binomials.(x2−3)(x2−7)=x4−7x2−3x2+21=x4−10x2+21.The expanded form matches the original expression, so the factoring is correct.
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